Symmetric Si/Si_1-xGe_x two-dimensional hole gases grown by rapid thermal chemical vapor deposition

Single and symmetric double p-type modulation-doped structures have been fabricated in Si/SiGe for the first time by rapid-thermal chemical-vapor deposition. Temperature-dependent electrical measurements and high-field magnetotransport measurements demonstrate the presence of a well-confined two-dimensional hole gas in these samples. Nominally-symmetric normal and inverted structures differ in carrier density and mobility at most by 20%, indicating that there is little asymmetry due to surface segregation or autodoping effects. Measurements on double heterostructures confirm that the interfaces are symmetric to within 10 Å. Peak mobilities reached 2500 cm²/V s at 10 K, comparable to those obtained in similar samples grown by ultrahigh vacuum techniques.